Impact of aging on gastrointestinal mucosal immunity.

There is considerable evidence that the mucosal or secretory immune response in the gastrointestinal tract is compromised by aging. The generation of a mucosal immune response is an extremely complex process that involves antigenic stimulation of a specific subpopulation of immunologically competent cells in the Peyer's patches, differentiation and migration of these cells to the small intestinal lamina propria, initiation and regulation of local antibody production in the intestinal wall, and mucosal epithelial cell receptor-mediated transport of antibodies to the intestinal lumen. Available data suggest that gastrointestinal mucosal immunosenescence reflects deficits in: (1) the differentiation and/or migration (homing) of immunoglobulin A immunoblasts to the intestinal lamina propria, and (2) the initiation and/or regulation of local antibody production. The significant age-related increases in the incidence and severity of gastrointestinal infectious diseases, coupled with the potential for immunopharmacologic manipulation of the mucosal immune compartment, substantiate the merit of studies designed to resolve the etiology of mucosal immunodeficiency in the elderly.